1. Field of the Invention
This invention relates generally to the drilling of deep wells such as for the production of petroleum products and more specifically concerns the supply of power to a remote receiver used to acquire subsurface formation data either while well drilling operations are in progress or during wireline logging.
2. Description of the Related Art
The oilfield service industry is currently attempting to measure more formation parameters while drilling. One method to achieve this objective is by the deployment in the formation of remote sensors. In order to collect and transmit data, these sensors must be either battery or remote powered. The main drawback of a battery-powered sensor is that its lifetime is relatively short, and once the battery is completely discharged, the remote sensor becomes useless.
Another solution is to transmit power to the sensor by using electromagnetic radio waves at high frequencies. In this case, one of the main difficulties is that while high frequency radio waves allow beam focusing through the formation, these radio waves are strongly attenuated by the formation fluids. In order to avoid the attenuation of these radio signals, it is preferable to use lower frequency radio waves. The problem then is that beam focusing becomes extremely difficult. Without beam focusing, the power emitted is radiated over a large volume instead of only toward the remote sensor and therefore, a large amount of the power emitted is lost. In order to compensate for this loss, the transmitter would have to be much more powerful.
For the foregoing reasons, there is a need for an apparatus and a method to remotely power a sensor located in a subsurface formation without being limited by a battery lifetime and without imposing unduly high power requirements on a downhole tool.
Accordingly, it is the general object of the present invention to provide a novel method and apparatus for remotely powering a receiver located in a subsurface formation.
It is an even further feature of the present invention to provide a novel method and apparatus for remotely powering a receiver without using electromagnetic radio waves to generate electricity.
It is still a further feature of the present invention to provide an apparatus which is simple in construction, yet effective to generate electricity in a receiver located in a subsurface formation.